A fiber-optic amplifier is a fiber-optic device that directly amplifies an optical signal without having to convert the optical signal into an electrical signal. Generally, a fiber-optic amplifier includes a length of optical gain fiber (e.g., optical fiber that is doped with a gain material) and a source of pump light (e.g., a pump laser diode). The pump light is coupled into the gain fiber along with an optical signal to be amplified. The gain material absorbs the pump light which promotes the gain material into an excited energy state, and the excited gain material provides optical amplification to the optical signal through stimulated emission. An optical signal that is amplified by a fiber-optic amplifier can include continuous-wave light or a series of optical pulses.
Light detection and ranging (lidar) is a technology that can be used to measure distances to remote targets. Typically, a lidar system includes a light source and an optical receiver. The light source can include, for example, a seed laser which emits light having a particular operating wavelength followed by a fiber-optic amplifier that amplifies the seed-laser light. The operating wavelength of a lidar system may lie, for example, in the infrared, visible, or ultraviolet portions of the electromagnetic spectrum. The light source emits light toward a target which then scatters the light. Some of the scattered light is received back at the receiver. The system determines the distance to the target based on one or more characteristics associated with the returned light. For example, the system may determine the distance to the target based on the time of flight of a returned light pulse.